This invention relates generally to rectilinear motion proportional solenoids and has application to solenoids which produce a motion-directed output which is linearly proportional to the electrical input current applied to the coil of the solenoid. More particularly, this invention is directed to the valve which is actuated by such solenoids.
This case is a companion to patent application Ser. No. 662,911, filed on Mar. 1, 1991, which is directed to an improved linear proportional solenoid which actuates the valve of preferred embodiment of the present invention. Both inventions have been assigned to the same assignee. The complete disclosure and specification of that pending application is specifically incorporated herein by reference.
Linear proportional solenoids are shown and described in U.S. Pat. Nos. 4,463,332; 4,767,097; and 4,835,503. In each of these patents, the permanent magnet whose magnetic field aids the magnetic field created by the electrical current-induced coil has various operative locations. In U.S. Pat. Nos. 4,463,332 and 4,767,097 the permanent magnet surrounds the coil. In U.S. Pat. No. 4,835,503 the permanent magnet is placed interiorly of the coil and located in the end face of the polepiece. In each of the aforementioned patents, there are two linear springs which are positioned within the flux path of the solenoid and which carry the moveable armature of the solenoid.
Particular attention is drawn to U.S. Pat. No. 4,767,097, which incorporates a spherical ball element slidably disposed within a cylindrical valve seat. While that design was an improvement over the prior art of that time, minor defects have been encountered and the present invention obviates these problems.
More specifically, it has been found that the ball has a tendency to flutter in its socket and does not always engage well with the valve seat. This causes a discontinuity of flow.
In the two embodiments described hereinafter, the valve seat is rigidly fixedly mounted in the flow path and the poppet is loosely secured to the valve stem such that the poppet is free to move in a lateral plane relative to the surface of the valve stem and to the surface of the valve seat.
It will be understood that, while the specific design and the components within the valve of the two embodiments are distinct, there is a principal involved which applies to both embodiments. That critical principal is that the poppets of each embodiment are secured to the valve stems by a magnetic means.
In one embodiment, the poppet is hemispherical in shape, as will be explained subsequently in detail, with its flat portion facing the valve stem. A magnet is secured in the face of the valve stem, and the poppet is free to move in a lateral direction in order to effect a more perfect seal between the hemispherical portion of the poppet and the valve seat.
In the second embodiment, the tip portion of the valve stem, i.e., facing the poppet, is a modified ball and socket joint, modified to the extent that the "ball" is a hemisphere, with the hemispherical surface facing inwardly and the flat surface facing toward the poppet. In this embodiment, the magnet is secured to the flat surface of the hemisphere and a mating ferromagnetic disc is imbedded into the surface of the poppet.
In this second embodiment, the surface of the valve seat is a conically shaped surface extending from the centrally located orifice. The poppet is also conically shaped, and has a cone angle which is substantially equal to the cone angle of the conically shaped valve seat. It is preferred that both cone angles are approximately 30.degree..
The poppets of both of the preferred embodiments of this invention are self-centering and self-aligning, forming a much improved valve and overcoming the aforementioned difficulties.